This invention relates generally to the integration of multiple types of local area networks (LANs) into a wide area network (WAN) using a set of protocols generally known as TCP/IP where TCP stands for Transmission Control Protocol, and IP is Internet Protocol. The invention provides multiple types of interconnection using PSTN (Public Switched Telephone Network) facilities to provide cost effective IP internetwork data transport. The system will provide an equal access model pursuant to the MFJ (Modified Final Judgment) and currently applicable statutes for accessing inter-LATA Internet carriers. The following background material introduces various computer network concepts and definitions and those familiar with computer networks and TCP/IP may wish to skip to following subsections.
A computer network is simply a collection of autonomous computers connected together to permit sharing of hardware and software resources, and to increase overall reliability. The qualifying term xe2x80x9clocal areaxe2x80x9d is usually applied to computer networks in which the computers are located in a single building or in nearby buildings, such as on a college campus or at a single corporate site. When the computers are further apart, the terms xe2x80x9cwide area networkxe2x80x9d or xe2x80x9clong haul networkxe2x80x9d are used, but the distinction is one of degree and the definitions sometimes overlap.
A bridge is a device that is connected to at least two LANs and serves to pass message frames or packets between LANs, such that a source station on one LAN can transmit data to a destination station on another LAN, without concern for the location of the destination. Bridges are useful and necessary network components, principally because the total number of stations on a single LAN is limited. Bridges can be implemented to operate at a selected layer of protocol of the network. A detailed knowledge of network architecture is not needed for an understanding of this invention, but a brief description follows by way of further background.
At the heart of any computer network is a communication protocol. A protocol is a set of conventions or rules that govern the transfer of data between computer devices. The simplest protocols define only a hardware configuration, while more complex protocols define timing, data formats, error detection and correction techniques and software structures.
Computer networks almost universally employ multiple layers of protocols. A low-level physical layer protocol assures the transmission and reception of a data stream between two devices. Data packets are constructed in a data link layer. Over the physical layer, a network and transport layer protocol governs transmission of data through the network, thereby ensuring end-to end reliable data delivery.
The most common physical networking protocol or topology for small networks is Ethernet, developed by Xerox. When a node possesses a packet to be transmitted through the network, the node monitors the backbone and transmits when the backbone becomes clear. There is no central backbone master device to grant requests to gain access to the backbone. While this type of multipoint topology facilitates rapid transmission of data when the backbone is lightly utilized, packet collisions may occur when the backbone is heavily utilized. In such circumstances, there is a greater chance that multiple nodes will detect that the backbone is clear and transmit their packets coincidentally. If packets are impaired in a collision, the packets are retransmitted until transmission is successful.
Another conventional physical protocol or topology is Token Ring, developed by IBM. This topology employs a xe2x80x9ctokenxe2x80x9d that is passed unidirectionally from node to node around an annular backbone. The node possessing the token is granted exclusive access to the backbone for a single packet transfer. While this topology reduces data collisions, the latency incurred while each node waits for the token translates into a slower data transmission rate than Ethernet when the network is lightly utilized.
As computer networks have developed, various approaches have been used in the choice of communication medium, network topology, message format, protocols for channel access, and so forth. Some of these approaches have emerged as de facto standards, but there is still no single standard for network communication. However, a model for network architectures has been proposed and widely accepted. It is known as the International Standards Organization (ISO) Open Systems Interconnection (OSI) reference model. The OSI reference model is not itself a network architecture. Rather it specifies a hierarchy of protocol layers and defines the function of each layer in the network. Each layer in one computer of the network carries on a conversation with the corresponding layer in another computer with which communication is taking place, in accordance with a protocol defining the rules of this communication. In reality, information is transferred down from layer to layer in one computer, then through the channel medium and back up the successive layers of the other computer. However, for purposes of design of the various layers and understanding their functions, it is easier to consider each of the layers as communicating with its counterpart at the same level, in a xe2x80x9chorizontalxe2x80x9d direction.
The lowest layer defined by the OSI model is called the physical layer, and is concerned with transmitting raw data bits over the communication channel. Design of the physical layer involves issues of electrical, mechanical or optical engineering, depending on the medium used for the communication channel. The layer next to the physical layer is called the data link layer. The main task of the data link layer is to transform the physical layer, which interfaces directly with the channel medium, into a communication link that appears error-free to the next layer above, known as the network layer. The data link layer performs such functions as structuring data into packets or frames, and attaching control information to the packets or frames, such as checksums for error detection, and packet numbers.
Although the data link layer is primarily independent of the nature of the physical transmission medium, certain aspects of the data link layer function are more dependent on the transmission medium. For this reason, the data link layer in some network architectures is divided into two sublayers: a logical link control sublayer, which performs all medium-independent functions of the data link layer, and a media access control (MAC) sublayer. This sublayer determines which station should get access to the communication channel when there are conflicting requests for access. The functions of the MAC layer are more likely to be dependent on the nature of the transmission medium.
Bridges may be designed to operate in the MAC sublayer. Further details may be found in xe2x80x9cMAC Bridges,xe2x80x9d P802.1D/D6, September 1988, a draft publication of IEEE Project 802 on Local and Metropolitan Area Network Standards, or in later drafts of this document.
The basic function of a bridge is to listen xe2x80x9cpromiscuously,xe2x80x9d i.e. to all message traffic on all LANs to which it is connected, and to forward each message it hears onto LANs other than the one from which the message was heard. Bridges also maintain a database of station locations, derived from the content of the messages being forwarded. Bridges are connected to LANs by paths known as xe2x80x9clinks.xe2x80x9d After a bridge has been in operation for some time, it can associate practically every station with a particular link connecting the bridge to a LAN, and can then forward messages in a more efficient manner, transmitting only over the appropriate link. The bridge can also recognize a message that does not need to be forwarded, because the source and destination stations are both reached through the same link. Except for its function of xe2x80x9clearningxe2x80x9d station locations, or at least station directions, the bridge operates basically as a message repeater.
As network topologies become more complex, with large numbers of LANs, and multiple bridges interconnecting them, operational difficulties can ensue if all possible LAN bridging connections are permitted. In particular, if several LANs are connected by bridges to form a closed loop, a message may be circulated back to the LAN from which it was originally transmitted, and multiple copies of the same message will be generated. In the worst case, messages will be duplicated to such a degree that the networks will be effectively clogged with these messages and unable to operate at all.
To prevent the formation of closed loops in bridged networks, IEEE draft publication P802.1D, referred to above, proposes a standard for a spanning tree algorithm that will connect the bridged network into a tree configuration, containing no closed loops, and spanning the entire network configuration. The spanning tree algorithm is executed periodically by the bridges on the interconnected network, to ensure that the tree structure is maintained, even if the physical configuration of the network changes. Basically, the bridges execute the spanning tree algorithm by sending special messages to each other to establish the identity of a xe2x80x9crootxe2x80x9d bridge. The root bridge is selected, for convenience, as the one with the smallest numerical identification. The algorithm determines which links of the bridges are to be active and which are to be inactive, i.e. disabled, in configuring the tree structure. One more piece of terminology is needed to understand how the algorithm operates. Each LAN has a xe2x80x9cdesignatedxe2x80x9d link, which means that one of the links connectable to the LAN is designated to carry traffic toward and away from the root bridge. The basis for this decision is similar to the basis for selecting the root bridge. The designated link is the one providing the least costly (shortest) path to the root bridge, with numerical bridge identification being used as a tie-breaker. Once the designated links are identified, the algorithm chooses two types of links to be activated or closed: first, for each LAN its designated link is chosen, and second, for each bridge a link that forms the xe2x80x9cbest pathxe2x80x9d to the root bridge is chosen, i.e. a link through which the bridge received a message giving the identity of the root bridge. All other links are inactivated. Execution of the algorithm results in interconnection of the LANs and bridges in a tree structure, i.e. one having no closed loops.
Internet is a collection of networks, including Arpanet, NSFnet, regional networks such as NYsernet, local networks at a number of university and research institutions, and a number of military networks. The protocols generally referred to as TCP/IP were originally developed for use only through Arpanet and have subsequently become widely used in the industry. The protocols provide a set of services that permit users to communicate with each other across the entire Internet. The specific services that these protocols provide are not important to the present invention, but include file transfer, remote log-in, remote execution, remote printing, computer mail, and access to network file systems.
The basic function of the Transmission Control Protocol (TCP) is to make sure that commands and messages from an application protocol, such as computer mail, are sent to their desired destinations. TCP keeps track of what is sent, and retransmits anything that does not get to its destination correctly. If any message is too long to be sent as one xe2x80x9cdatagram,xe2x80x9d TCP will split it into multiple datagrams and makes sure that they all arrive correctly and are reassembled for the application program at the receiving end. Since these functions are needed for many applications, they are collected into a separate protocol (TCP) rather than being part of each application. TCP is implemented in the transport layer of the OSI reference model.
The Internet Protocol (IP) is implemented in the network layer of the OSI reference model, and provides a basic service to TCP: delivering datagrams to their destinations. TCP simply hands IP a datagram with an intended destination; IP is unaware of any relationship between successive datagrams, and merely handles routing of each datagram to its destination. If the destination is a station connected to a different LAN, the IP makes use of routers to forward the message.
TCP/IP frequently uses a slight deviation from the seven-layer OSI model in that it may have five layers. These five layers are combinations and derivatives of the seven-layer model as shown in FIG. 1. The five layers are as follows:
Layer 5xe2x80x94The Application Layer. Applications such as ftp, telnet, SMTP, and NFS relate to this layer.
Layer 4xe2x80x94The Transport Layer. In this layer, TCP and UDP add transport data to the packet and pass it to layer 3.
Layer 3xe2x80x94The Internet Layer. When an action is initiated on a local host (or initiating host) that is to be performed or responded to on a remote host (or receiving host), this layer takes the package from layer 4 and adds IP information before passing it to layer 2.
Layer 2xe2x80x94The Network Interface Layer. This is the network device as the host, or local computer, sees it and it is through this medium that the data is passed to layer 1.
Layer 1xe2x80x94The Physical Layer. This is literally the Ethernet or Serial Line Interface Protocol (SLIP) itself.
At the receiving host the layers are stripped one at a time, and their information is passed to the next highest level until it again reaches the application level. If a gateway exists between the initiating and receiving hosts, the gateway takes the packet from the physical layer, passes it through a data link to the IP physical layer to continue, as is shown in FIG. 2. As a message is sent from the first host to the second, gateways pass the packet along by stripping off lower layers, readdressing the lower layer, and then passing the packet toward its final destination.
A router, like a bridge, is a device connected to two or more LANs. Unlike a bridge, however, a router operates at the network layer level, instead of the data link layer level. Addressing at the network layer level makes use of a 32-bit address field for each host, and the address field includes a unique network identifier and a host identifier within the network. Routers make use of the destination network identifier in a message to determine an optimum path from the source network to the destination network. Various routing algorithms may be used by routers to determine the optimum paths. Typically, routers exchange information about the identities of the networks to which they are connected.
When a message reaches its destination network, a data link layer address is needed to complete forwarding to the destination host. Data link layer addresses are 48 bits long and are globally unique, i.e. no two hosts, wherever located, have the same data link layer address. There is a protocol called ARP (address resolution protocol), which obtains a data link layer address from the corresponding network layer address (the address that IP uses). Typically, each router maintains a database table from which it can look up the data link layer address, but if a destination host is not in this ARP database, the router can transmit an ARP request. This message basically means: xe2x80x9cwill the host with the following network layer address please supply its data link layer address.xe2x80x9d Only the addressed destination host responds, and the router is then able to insert the correct data link layer address into the message being forwarded, and to transmit the message to its final destination.
IP routing specifies that IP datagrams travel through internetworks one hop at a time (next hop routing) based on the destination address in the IP header. The entire route is not known at the outset of the journey. Instead, at each stop, the next destination (or next hop) is calculated by matching the destination address within the datagram""s IP header with an entry in the current node""s (typically but not always a router) routing table.
Each node""s involvement in the routing process consists only of forwarding packets based on internal information resident in the router, regardless of whether the packets get to their final destination. To extend this explanation a step further, IP routing does not alter the original datagram. In particular, the datagram source and destination addresses remain unaltered. The IP header always specifies the IP address of the original source and the IP address of the ultimate destination.
When IP executes the routing algorithm it computes a new address, the IP address of the machine/router to which the datagram should be sent next. This algorithm uses the information from the routing table entries, as well as any cached information local to the router. This new address is most likely the address of another router/gateway. If the datagram can be delivered directly (the destination network is directly attached to the current host) the new address will be the same as the destination address in the IP header.
The next hop address defined by the method above is not stored in the IP datagram. There is no reserved space to hold it and it is not xe2x80x9cstoredxe2x80x9d at all. After executing the routing algorithm (the algorithm is specific to the vendor/platform) to define the next hop address to the final destination. The IP protocol software passes the datagram and the next hop address to the network interface software responsible for the physical network over which the datagram must now be sent.
The network interface software binds the next hop address to a physical address (this physical address is discovered via address resolution protocols (ARP, RARP, etc.), forms a frame (Ethernet, SMDS, FDDI, etc.xe2x80x94OSI layer 2 physical address) using the physical address, places the datagram in the data portion of the frame, and sends the result out over the physical network interface through which the next hop gateway is reached. The next gateway receives the datagram and the foregoing process is repeated.
In addition, the IP does not provide for error reporting back to the source when routing anomalies occur. This task is left to another Internet protocol, the Internet Control Message Protocol (ICMP).
A router will perform protocol translation. One example is at layers 1 and 2. If the datagram arrives via an Ethernet interface and is destined to exit on a serial line, for example, the router will strip off the Ethernet header and trailer, and substitute the appropriate header and trailer for the specific network media, such as SMDS, by way of example.
A route policy may be used instead of routing table entries to derive the next hop address. In the system and methodology of the present invention, the source address is tested to see in which ISP address range it falls. Once the ISP address range is determined the packet is then routed to the next hop address associated with the specific ISP.
Data communications network services have two categories of call establishment procedures: connection-oriented and connectionless.
Connection-oriented network services require that users establish a single distinct virtual circuit before the data can be transmitted. This circuit then defines a fixed path through the network that all traffic follows during the session. Several packet switching services are connection-oriented, notably X.25 and Frame Relay. X.25 is the slower of the services, but has built-in error correctionxe2x80x94enough for its performance not to depend on clean, high-quality optical fiber lines. Frame relay, regarded as the first generation of fast packet technology, is well-suited for high-speed bursty data communication applications.
Connectionless network services, by contrast, let each packet of a communications session take a different, independent path through the network. One example is the Switched Multimegabit Data Service (SMDS), a possible precursor to broadband ISDN. This fast-packet service supports data rates ranging from the T1 rate of 1.544 Mb/s up to 1 Gb/s. The SMDS transport system architecture is defined by IEEE 802.6 Metropolitan Area Network standards.
SMDS supports LAN interconnection and allows the transfer of large, variable length service data units (SDUs). Like frame relay, SMDS allows the user to connect multiple remote routers without having to employ a mesh network. However, as compared to frame relay, SMDS affords a number of advantages. Among these are that it is a connectionless service better suited for LAN traffic, it supports higher access rates and throughput for evolving applications (DS3 and SONET), it supports higher burstiness, and SMDI""s cell relay technology implies that it will migrate smoothly to BISDN.
The process of routing packets over the Internet is also considered a connectionless network service. The Internet Protocol (IP) addresses packets from sender to receiver. It is still used mostly in conjunction with the Transmission Control Protocol (TCP), which establishes a connection between end users to manage the traffic flow and ensures the data are correct, providing end-to-end reliability. The combination, known as TCP/IP, is the Internet""s main backbone protocol suite.
Asynchronous transfer mode (ATM) is a connection-oriented network service. It is a high-bandwidth, fast-packet switching and multiplexing technique that segments packets into 53-byte cells. It supports sound (voice and audio), data, documents (text, graphics and still images), and video (moving pictures with sound). ATM and SDH/SONET are key technologies enabling broadband ISDN.
The Internet has outgrown its academic origins to become a working version of the global information infrastructure and use of the Internet Protocol (IP) has become widespread. A broad spectrum of companies are indicating an interest and belief in the Internet""s potential for a wide variety of services and are desirous of using IP for internetwork communication. An almost limitless scope of data exchange is under current investigation for transfer between varying types of LANs, MANs (metropolitan area networks) and WANs using both connection oriented and connectionless procedures of numerous types. Each procedure has its advocates and perceived advantages and disadvantages, and is currently in use to at least some extent. In this evolutionary stage there is a need for a cost effective IP transport system that can accommodate these plural procedures and approaches on a widespread geographic basis.
Perlman et al. U.S. Pat. No. 5,309,437 issued May 3, 1994, entitled xe2x80x9cBridge-Like Internet Protocol Routerxe2x80x9d. The patent pertains to local area networks (LANs) of computers and to multiple LANs that are interconnected by bridges and routers. The patent is directed to a problem that arises in interconnected networks using the TCP/IP protocols. A bridge is defined as a device that connects at least two LANs and serves to pass message frames or packets between LANs so that a source station on one LAN can transmit data to a destination station on another LAN without concern for the location of the destination. A router is defined in the patent as a device connected to two or more LANs that operates at the network level layer. A data link layer address is needed to complete forwarding a message to the destination host after the message reaches its destination network. ARP (address resolution protocol) obtains a data link layer address from the corresponding network layer address. ARP messages are said to cause problems when bridges are used within an extended network of LANs. ARP packets can be duplicated by bridges and this can result in xe2x80x9cflurriesxe2x80x9d of ARP packets which can disrupt normal traffic flow.
The patent proposes the solution of using a bridge-like IP router called a BLIP. This functions like a bridge for non-TCP/IP traffic and functions in a bridge-like manner for TCP/IP traffic. It functions like a bridge at the network layer level of addressing.
The method of the patent includes configuring an extended local area network (LAN) to include a plurality of extended LAN segments connected to bridge-like IP routers (BLIPs). These receive a packet of data at a BLIP and determine whether the packet has been transmitted under TCP/IP protocols. Non-TCP/IP packets are processed in the manner of a conventional bridge and TCP/IP traffic is processed in a manner analogous to a bridge.
Baudoin U.S. Pat. No. 5,406,557 issued on Apr. 11, 1995, is entitled xe2x80x9cInterenterprise Electronic Mail Hubxe2x80x9d. The patent relates to electronic mail on wide area networks and includes multiple incompatible electronic mail applications. The patent deals primarily with the transmission of E-Mail and enables users located in different locales to use different E-Mail Protocols.
The patent utilizes an electronic communication center (ECC) that serves as a hub for routing messages. The ECC has a message queue, a queue management system, an address table and a plurality of translation modules. The ECC converts all incoming E-Mail messages to a non-user specific standard protocol. Then, based upon the destination address, the ECC converts the nonstandard protocol to the appropriate protocol for each destination user. FIG. 1 illustrates an embodiment of the invention. In that figure the block 2 represents an enterprise which includes various internal entities 4, 6, 8, and 10 connected to users located outside of enterprise 2. This communication equipment connects to a communications hub 14 which may be a mainframe or mini-computer. Hub 14 contains a plurality of communication modules useful for interfacing with individual pieces of communications equipment.
Each piece of communication equipment internal to enterprise 2 connects to one of the internal communication modules 16. Network interfaces and communication equipment external to enterprise 2 connect to one of the external communication modules 18. Thus, hub 14 is divided into two halves, an internal communication half 14a and an external communication half 14b. The internal communications module 16 converts messages and information data between a xe2x80x9cuniversalxe2x80x9d format and protocol internal to hub 14 and the protocol and format used by the associated piece of communications equipment. Hub 14 look at the destination address for a message received from one of the entities 4, 6 or 10 and routes the message to the appropriate external communication module 18. Module 18 converts the universal format message into the specific message format and protocol required by the end user. For example, module 18a connects to the Internet.
Callon U.S. Pat. No. 5,430,727 issued Jul. 4, 1995. The patent deals with calculating routes for sending user data packets through an interconnected network of information handling devices. It utilizes two protocol suites. One is the OSI-I and the other is the TCP/IP. The patent allows data packets to be forwarded from one local area network to another by a device acting as a router and allows the first protocol suite to act as a bridge rather than a router.
It is a primary object of the present invention to provide a system and method for meeting the above described need and solving the problem which it presents.
It is another object of the invention to meet this need using plant, facilities and technologies which are individually available to a large extent in the public switched telephone network (PSTN).
It is yet another object of the invention to accomplish the foregoing in a fashion which presents cost advantages to both users and providers of the involved services.
It is another object of the invention to provide such a system and method which will permit customers to be able to access information through a variety of communication facilities offering service at multiple selectable speeds of access and different types of connectivity.
It is a further object of the invention to provide such a system through use of the public switched telephone network using an equal access model and source routing.
In a simplified sense the present invention is directed to providing a common carrier platform and methodology for implementing access to the Internet and related IP data transport service for users or customers employing a wide variety of procedures and intranetwork protocols. The target customers for the service constitute Internet Service Providers (ISPs) as well as intranet users such as small and large corporations who wish to use IP in support of their corporate networks. In this sense the invention involves supplying IP transport service and a Telco maintained and operated IP transport network. In another sense the invention provides Internet access to widespread local areas served by a public switched telephone network. In the latter example a consumer access provider company, which may or may not be Telco owned, may obtain access to Telco customers virtually throughout its operating region. This may be accomplished according to the invention without violation of the currently existing judicial and regulatory proscription of inter-LATA message service by a regional Telco.
Customers may obtain the use of various types of ports on the Telco platform such as, by way of example, analog 28.8 Kb/s service, ISDN service, dedicated ports for SMDS (switched multimegabyte data service), frame relay, T1, DDS or other available services. As a matter of convenience the hubs will be collocated with central office switching systems and oftentimes may be sited in the same building. Each hub and its equipment will be operated, maintained and provisioned by Telco personnel.
The current availability of the Telco SMDS service, with its previously described advantages, makes feasible virtually immediate provision of service to large business customers capable of interfacing via SMDS. This facilitates limitation of the load or traffic on the gateway routers in the hubs inasmuch as the SMDS signals may be bypassed around the router.
A key component of the system is the LATA hub wherein one such hub is provided for each LATA. In one Telco example 19 such LATA hubs are utilized. Dedicated access is offered only from such LATA hubs and will support connectionless services such as frame relay or SMDS, which are currently tariffed fast packet services which are non-distance sensitive. Other presently tariffed services also will be available from these LATA hubs, such as DDS or T1, however these services involve point to point circuits which require additional hardware and are distance sensitive. The system of the invention would allow Internet service provider customers such as UUNet, PSI, and the like, to concentrate on providing service, which is the source of their income, and refrain from investing capital in infrastructure and infrastructure provisioning and maintenance.
The main module of equipment in the hub is the gateway router. The gateway router is connected via redundant links to the Telco LATA SMDS network or xe2x80x9ccloudxe2x80x9d and thence to the Internet at large. The SMDS links may be 34 Mb/s or T1 links or any combination thereof or of similar links.
The Internet Protocol Routing Service (IPRS) of the invention provides for the collection, concentration and management of the customers traffic within a LATA. IP Routing Service comprises network routers located at LATA hub sites that will collect the customer""s (ISP""s) end user traffic and concentrate it for connection and transport over a Telco Exchange Access Switched Multi-Megabit Data Service (XASMDS) Subscriber Network Interface. By way of example,the IP routing service may provide six types of ports for the collection of end user traffic. The port type or types are determined by the method chosen by the customer for access to its end users. The six port types may be analog dial-up, Integrated Services Digital Network (ISDN) dial-up, Digital Data Service (DDS), DSl (Digital Service, level 1), 56 kbps Frame Relay, and 1.544 Mbps (Txe2x88x921) Frame Relay. The IP Routing Service may use RADIUS (Remote Authentication Dial-in User Service) as a network security protocol, for the customer""s (ISP""s) authentication and authorization of the ISP""s dial-up end users. The reference to six port types is exemplary only and additional port types may be added within the scope of the invention.
Another advantage is that when connections are made under the SMDS cloud it is not necessary to pass that traffic through the gateway router in the cognizant hub to get to the Internet. The customer can peer directly to their Internet carrier of choice, their ISP of choice. If frame relay switches were being used there would not be a direct peer relationship. It would be necessary to pass through a central site router at some point. This would create congestion in the gateway router.
Traffic from a customer""s switched access end users passes through the central office switching system with which the mini-hub or the LATA hub is collocated. This traffic passes from the central office switch to communication access servers (sometimes referred to herein as access servers or network access servers or NASs) and thence to an Ethernet packet switch in the hub. The access servers perform on a more limited scale the same functionality as the gateway router. Thus the access servers deliver the physical PRI on the central office switch side as 10baseT to the Ethernet switch, the translation having occurred in the access server. The access servers handle either POTS (Plain Old Telephone Service) or ISDN (Integrated Service Digital Network) signals. The Ethernet switch performs further concentration and switching to a 100baseT link to the gateway router. The gateway router in turn acts as an IP packet switch and routes the traffic to the SMDS network or cloud. The gateway router performs the same packet switch function to route SMDS to frame relay or to route Ethernet to frame relay or the converse.
It is an important feature of the invention that source routing may be implemented.
Each LATA hub and each mini-hub has an administrative router to provide for maintenance. It is a further feature of the invention that a maintenance backbone network is provided to troubleshoot and maintain the entire network. The administrative router has access to all of the different modules of equipment in the hub and network both through the SMDS network as well as through a frame relay overlay network to a central Telco maintenance center. The frame relay cloud serves as a maintenance backbone network and traverses all 80 hub sites in this example. Inasmuch as this performs a management function the communication across LATA boundaries is permissible under applicable regulations. According to the invention the operation of the entire network is monitored using SNMP (simplified network management protocol). When trouble is detected via the SMDS network, this is further analyzed using the frame relay backup network. Correction is effected through the frame relay network.
The maintenance center includes a server or router and a group of terminals providing interfaces to the SMDS and frame relay networks. A technician at a terminal at the maintenance site may control trouble shooting and provide centralized maintenance of the entire IPRS network. The overlay network is used to provide automated management and maintenance functions beyond routine monitoring. The frame relay network is entirely private and provides secure addressing and levels of security not readily available via the main SMDS cloud. Whereas certain monitoring occurs via SNMP this constitutes a read only feature. The write function is reserved for the private frame relay network.